As far as ethernet cables and network isolation devices, here is what I found with the mR connected to my DAVE.
Having tried various inexpensive CAT 5/6 cables in the past (I've not tried CAT 7/8 cables), I never could tell much of a difference with my previous TotalDac setup although I had settled on the Blue Jeans brand of Belkin-made network cables (the blue cable in the photo) over a generic CAT 6 cable (skinny white cable in the photo) that is included for free with your router or network device as the Blue Jeans cable felt very well made in comparison with good shielding and superior connectors. Their CAT 6 cables also came with performance measurements which I felt was a nice touch. I once tried an AudioQuest Cinnamon ethernet cable and heard no difference against the much less expensive Blue Jeans cable and so it had been my opinion that expensive audiophile network cables were snake oil.
Then, someone sent me an SOtM CAT6 cable ($170) with isolation filter ($350) (the thick white cable in the photo) last year and this made a very noticeable improvement in terms of clarity and more open soundstage over the Blue Jeans cable. This was the first cable that proved to me that network isolation or RF filtration mattered and so this had become my reference network cable. At some point, I was introduced to optical isolators and just like a Toslink SPDIF data cable, it did a great job of isolating against line noise. Combined with my SOtM network cable/filter, I felt pretty comfortable that I was adequately isolated from network line noise and indeed, I couldn't tell much difference between local playback vs network Tidal streaming with my former CAD CAT server.
As has been described by John Swenson, the mR has various defenses against network RF noise including a combination of methods to both isolate and filter against this noise. In Chris Connaker's review, he was unable to distinguish among various inexpensive network cables but admitted that he had not tried any expensive "audiophile" network cables nor did he make mention whether he assessed for the impact of optical network isolators.
In my testing, I did find some differences although they are minor. What surprised me more was what my preference was. What I found was that my optical isolators now don't add much, if anything at all. I thought at times I could be hearing a subtle difference but I also knew I could be imagining it. Upon blind testing, I could not tell at all. I have read on the CA site how one person actually felt his isolators made his SQ worse and so he removed them. With or without them, I could not detect a difference and so I have now removed them as well.
Between a cheap 3-foot CAT 6 cable that I got for free with one of my routers and a much better shielded Blue Jeans brand CAT6 cable with superior terminations (3 feet, $9.25), I could tell no difference. With the much more expensive SOtM cable ($170) + filter ($350), there was a definite "smoothing" effect that was unmistakable even when blinded but unlike with the Sonicorbiter or Aurender N10 where I found this effect preferable, with the mR, I did not. It almost seemed to rob some of the dynamics from the music and took away some of that "you are there" experience. This will probably come down to personal preference for some but for the first time, I am preferring a cheap cable against a proven, more expensive cable. Is it possible that too much conditioning is bad? Can putting a line conditioner after another line conditioner be too much? I will revisit this again down the road just to be sure but for now, I have decided to shelf my SOtM cable + filter and replace it with a Blue Jeans CAT 6.